chem 106 test 4

Question 1

four zones of a weak acid titration and how to calculate

Answer 1

1. initial - ICE table for the acid
2. before equivalence point - Henderson Hasselbach
3. at equivalence point - ICE table b/c all acid has been used up
4. after equivalence point - all strong base (weak base is trivial) so do -log[OH-]

Question 2

how to choose an indicator

Answer 2

changes color a little after the equivalence point

Question 3

how to write balanced equation for solubility

Answer 3

NaCl (s) -> Na+(aq) + Cl-(aq)

Question 4

Ksp equation

Answer 4

ex: NaCl (s) -> Na+(aq) + Cl-(aq)

Ksp = [Na+][Cl-]

Question 5

how to solve for molar solubility

ex: AB2 -> A^2+ + 2B^-

Answer 5

Ksp = (x)(2x)^2

x will give you M

Question 6

When is a solution saturated? supersaturated?

Answer 6

Q = Ksp -> saturated

Q > Ksp -> supersaturated (some will precipitate out)

Question 7

ΔG equation we have to have memorized

Answer 7

ΔG = ΔH - TΔS

Question 8

ΔS = +

Answer 8

more disorder

Question 9

ΔS = -

Answer 9

more order

Question 10

S is greater for (gases/liquids/solids)

Answer 10

gas > liquid > solid

disorder -> order

Question 11

ΔG = -

Answer 11

spontaneous

Question 12

ΔG = +

Answer 12

nonspontaneous (spontaneous in the opposite direction)

Question 13

ΔG = 0

Answer 13

equilibrium

Question 14

ΔH = - (exothermic) and ΔS = + (more disorder)

Answer 14

spontaneous at all temperatures

Question 15

ΔH = + (endothermic) and ΔS = - (more order)

Answer 15

nonspontaneous at all temperatures

Question 16

ΔH = - (exothermic) and ΔS = - (more order)

Answer 16

spontaneous at low temperatures

nonspontaneous at high temperatures

Question 17

ΔH = + (endothermic) and ΔS = + (more disorder)

Answer 17

nonspontaneous at low temperatures

spontaneous at high temperatures

Question 18

for the Nernst equation ΔG = ΔG* + RTlnQ, a small Q indicates a shift (left/right) and a large Q indicates a shift (left/right)

Answer 18

right - ΔG decreases so more spontaneous; left - ΔG increases so more nonspontaneous

Question 19

if ΔG* is negative, Keq is

Answer 19

large

Question 20

if ΔG* is positive, Keq is

Answer 20

small

Question 21

OIL RIG

Answer 21

oxidation is losing e-s (increase in oxidation number)

reduction is gaining e-s (decrease in oxidation number)

Question 22

to balance half reactions,

Answer 22

1. balance the atoms in each half reaction first
2. balance the electrons in each half reaction
3. multiply the full equations by the LCM to balance the total number of electrons

Question 23

oxidation occurs at the ? and reduction occurs at the ?

Answer 23

anode; cathode

AN OX, RED CAT

Question 24

the cathode (gains/loses) mass

Answer 24

loses - ionizing

Question 25

the anode (gains/loses) mass

Answer 25

gains - solidifying

Question 26

positive voltage, electrons flow from

Answer 26

anode to cathode

Question 27

an Ampere is a

Answer 27

Coulomb/sec

Question 28

Faraday’s constant is in units of

Answer 28

Coulombs/mol e-

Question 29

E*cell =

Answer 29

Ered, cathode - Ered, anode

Question 30

E*cell = +

Answer 30

spontaneous

Question 31

E*cell = -

Answer 31

nonspontaneous

Question 32

spontaneous reaction in terms of Ecell, ΔG, and Keq

Answer 32

Ecell +
ΔG -
Keq big

Question 33

nonspontaneous reaction in terms of Ecell, ΔG, and Keq

Answer 33

Ecell -
ΔG +
Keq small

Question 34

elements on the top right of the periodic table are strong ? agents

Answer 34

oxidizing (more electronegative means wants to be reduced more)

Question 35

elements on the bottom left of the periodic table are strong ? agents

Answer 35

reducing (want to be oxidized)

Question 36

batteries die when

Answer 36

they are at equilibrium; Ecell = 0 V

Question 37

Electrolysis: if E*cell is a negative voltage,

Answer 37

you can put that many volts into the system to make that reaction occur

Question 38

work: 1 J =

Answer 38

C * V

Question 39

kWhr =

Answer 39

3.6 x 10 ^ 6 J